@David-TP Thanks David.

[David]: Did all your devices have the same issue with Whatsapp Audio/Video calls? Have you got any error messages when they are not working?

[Atul]: I have tried from two different cell phones (unfortunately both were iPhones) and faced the same issue on both these devices.  

Person who is calling me -> On his/her phone it simply shows "ringing" and on my phone it shows "connecting state" & when i am calling someone it simply shows "ringing" on my phone and "connecting" on the other person's cell. After the call gets disconnected, It does display an message:

"Your Wifi Network prevents whatsapp calls  OR your phone's local network Access setting is disabled. Turn off wifi or enable access settings in Settings->Privacy->Local Network -> Whatsapp and try again"

Please note that Local Network Permissions are already enabled for whatsapp and it works fine if i replace my router.

[David]: And did you also try to turn off the "Mesh Technology" on the devices?

[Atul]: I am not getting any option to disable the Mesh Topology. Is there any thread where i can find this info.

Please note that i have directly connected my Deco with the Modem and it is working as a router, not the repeater/extender. 

By the way, there is no option to turn off the HomeSheild service and may I know what you have tried to turn it off?

[Atul]: Actually i have simply canceled my Home Shield subscription for a temporary period but not sure if it is going to disable it or not.

Whatsapp Response was still the same during that period and later i have reactivated my subscription again.

Regards,
Atul Gupta